Nanotubes seen emitting near-IR light

A team of Rice University chemists, led by Nobel Laureate Professor Richard Smalley, has discovered that carbon nanotubes emit near-IR light after absorbing light at visible or ultraviolet wavelengths. These properties could have nanoelectronics and biomedical applications.

Bruce Weisman, Professor of Chemistry at Rice, and a long-time colleague of Prof Smalley said: "Over the past year or so we have been collaborating with Prof Smalley in his nanotube research program. His lab grows the nanotubes from carbon monoxide and prepares samples of isolated tubes in aqueous micelles. The fluorescence measurements and interpretations are then made in my lab."

Nanotubes can be built in a variety of diameters, and each size has its own characteristic absorption and emission wavelengths.Professor Weisman outlined some of the possible applications for his team's findings: "The discovery of fluorescence opens many new approaches and tools to researchers working on the basic properties or possible applications of nanotubes. We expect that fluorescence will provide a very sensitive and selective method for detecting nanotubes in environmental and biological systems. It may lead to the use of nanotubes as biomedical contrast agents for non-invasive imaging of particular types of cells."

Prof Weisman also suggested that electrically excited nanotubes could be light emitters in a future generation of nanoscale integrated circuitry (nano-optoelectronics).

The next step for the team is to "assigning" the spectra - this involves investigating, exactly which nanotube structure gives each absorption and emission peak in the spectra.

According to Professor Weisman, the team has made substantial progress toward this important goal, and is currently preparing another report for publication.

"After that, we will be able to use quick spectroscopic methods to determine which structures are present in bulk nanotube samples. At present, such information is only barely available after very tedious analysis with the most advanced and expensive microscopic methods. This analytical method should enable advances in efforts to isolate nanotubes of particular structures."

Nanotube fluorescence was first found in Professor Weisman's lab late last October. The team then spent several months confirming and extending the observations before submitting their report to Science.

"This project has been a very fruitful collaboration that brought together the complementary capabilities of two research groups to make an important advance," said Professor Weisman.